1. Field of the Invention
The present invention relates to an electron beam irradiation apparatus and electron beam irradiation method for irradiating electron beams and to an apparatus for and a method of manufacturing a disc-shaped object.
2. Description of the Prior Art
Optical discs such as a CD (Compact Disc), a DVD (Digital versatile Disc), and the like have hitherto been utilized as optical information recording mediums. Over the recent years, however, there has been a progress of developing a blue semiconductor laser of which an oscillation wavelength is on the order of 400 nm. The development of a next generation high-density optical disc such as a high-density DVD, and the like capable of recording with a higher density than the general DVD, is conducted by use of this type of blue semiconductor laser.
FIG. 13 shows an example of a prior art layer structure of this type of next generation high-density optical disc.
This high-density optical disc is structured such that a recording layer 91 for recording information, a light transmitting layer 92 that transmits laser beams for recording and reproducing so that the laser beams get incident on the recording layer 91 and a protection layer 93 taking contact with a member on the side of an optical pickup into consideration, are stacked in this sequence on a substrate 90 composed of a resin material such as polycarbonate. The light transmitting layer 92 and the protection layer 93 are, when formed, irradiated with ultraviolet rays after being coated for curing. When especially the protection layer, etc. is formed of a material such as silicon compound, fluorine compound, etc. that exhibit radial polymerization double-bond, however, there might be a case in which a characteristic as the protection layer, etc. deteriorates unless a reaction initiator is added thereto in such a case, and the protection layer is hard to be cured by the irradiation of the ultraviolet rays, with the result that the protection layer having a sufficient quality can not be formed (refer to Japanese Patent Laid-Open Application Publication No.4-019839, Japanese Patent Laid-Open Application Publication No.11-162015, Japanese Patent Laid-Open Application Publication No.7-292470, Japanese Patent Laid-Open Application Publication No.2000-64042).
For solving the problems inherent in the prior arts given above, the present inventors cooperating with other inventors proposed an electron beam irradiation apparatus and an electron beam irradiation method in Japanese Patent Application No.2002-274120, which are capable of efficiently irradiating electron beams, of which an acceleration voltage is on the order of 20 kV through 100 kV while rotating a disc substrate, exhibiting consequently greater energy than the ultraviolet rays have, and of easily curing the protection layer, etc. such as a lubricating layer, etc. that is hard to be cured by the irradiation of the ultraviolet rays. In this case, a plurality of electron beam irradiation tubes are disposed for irradiating uniformly the whole disc substrate with the electron beams.
If the electron beam irradiation apparatus involves using the plurality of electron beam irradiation tubes, the apparatus increases both in weight and in size, an equipment cost rises because of the electron beam irradiation tube being comparatively expensive, and a running cost increases with a rise in amounts of consumption of an N2 gas for cooling and of electric power. A manufacturing cost increases due to these factors.